The present invention relates to a process for the production of a hydrolysate, in particular the production of hydrolysate by the biological hydrolysis of a protein containing material. The various forms of the hydrolysate can be used as a sauce, seasoning agent, or a base for culinary products.
Hydrolyzed proteins in the form of a soya sauce have been used as seasonings in food systems for centuries in the Far East. Traditionally the soya sauce was prepared by fermentation for a long period of time, usually several months. In producing soya sauce, plant protein containing materials such as cooked soya beans or defatted soy grits together with carbohydrates are inoculated with Aspergilli and the semi solid product is fermented for 2 days to make a Koji. During this time enzymes are produced that are able to hydrolyze the protein and carbohydrates in a second stage, called the moromi stage. The fermented Koji is mixed with a solution of common salt to provide the moromi, which is then fermented for 4 to 8 months by the soya lactic acid bacteria and soya yeasts. The soya sauce is obtained by removing the insoluble fractions from the fermented moromi.
About 100 years ago, a more rapid method of hydrolyzing proteins to produce seasonings was developed. This method uses hydrochloric acid and the time required for hydrolysis is only a few hours. In recent years, however, the use in culinary applications of acid hydrolyzed plant protein (HPP) has been under criticism due to the presence of chloro-compounds that arise from the acid process. Therefore, attempts have been made to develop HPP replacements that can be used as body-givers in culinary applications. Soya sauce is one such suitable replacement.
HPP and soya sauce, however, are not the same. For example, there are differences in the chemical composition and flavor profile of HPP and soya sauce owing to the differences in the raw materials and the processing methods involved. In addition, the dosage or amount of soya sauce that can be used as an HPP replacement is also limited due to its xe2x80x9cfermentedxe2x80x9d note. Furthermore, the different processing procedures results in a significant variation in the degree that the protein containing materials are hydrolyzed to amino acids. Also soya sauce has a lower amino acid content than HPP that leads to a significantly weaker body in soya sauce than in HPP. Thus, there is a need in the culinary field for improved HPP replacements such as soya sauce.
The present invention relates to a process for production of a hydrolysate as well as to the hydrolysates thus produced and their use in culinary products. The process includes fermenting a Koji substrate that contains a protein containing material and a carbohydrate that has been inoculated with a culture of a lactic acid bacteria that is capable of imparting a specific characteristic note to the hydrolysate at an inoculation density of from about 103 to 107 cfu/g of fermented Koji to produce a fermented Koji. Next, the fermented Koji is hydrolyzed at a temperature of between about 2xc2x0 C. and 50xc2x0 C. and a pH of from about 5.6 to 7, and preferably 5.8 to 6.6, for a period of from about 1 to 20 days to produce the hydrolysate. The hydrolysate has a characteristic note that is stronger than if the inoculation with the lactic acid bacteria occurred after the fermentation stage.
The lactic acid bacteria may be L. sake, L. plantarum, L. cuvatus, or a mixture thereof. The Koji may be fermented by inoculating a culture bed of the protein containing material and the carbohydrate with a culture of Aspergillus oryzae, Aspergillus sojae, or a mixture thereof.
The protein containing material may be a plant protein material containing cysteine in an amount of between about 0.5 to 3% by weight of the protein containing material. The protein containing material may be selected from the group consisting of soya, wheat germ, corn gluten, rice gluten, wheat gluten, or a mixture thereof. The amount of protein containing material in the Koji substrate may be from about 30 to 100% and preferably from about 70 to 90%. The protein containing material may be cooked and in solid particulate form. In one embodiment the protein containing material is fermented in the solid state.
Hydrolysis of the fermented protein Koji may be carried out in the presence of water and in the absence of salt. When the hydrolysis is carried out in the presence of water and in the absence of salt it may be carried out at a temperature of between about 30xc2x0 to 37xc2x0 C. for a period of between about 2 to 5 days. The hydrolysis of the fermented protein Koji may also be carried out in the presence of water and in the presence of salt in an amount of up to about 100% by weight based on the weight of the fermented Koji.
The hydrolysis may also be carried out in stages. In one embodiment, the hydrolysis is carried out in a first hydrolysis stage at a temperature of from about 40xc2x0 to 25xc2x0 C. for a period of from about 1 to 48 hours and then a second hydrolysis stage at a temperature of from about 25xc2x0 to 50xc2x0 C. for a period of from about 1 to 20 days.
In another embodiment, an additional protein that contains cysteine in an amount of between about 0.5 and 3% by weight of the protein is added to the fermented Koji at the beginning of the hydrolysis.
The hydrolysate may be pressed to separate a liquid sauce from a solid residue. The present invention also relates to the liquid sauce prepared by pressing the hydrolysate The liquid sauce may be pasteurized at a temperature of from about 90xc2x0 to 140xc2x0 C. for a period of from about 15 seconds to 30 minutes and filtered to give a liquid seasoning. The present invention also relates to the liquid seasoning prepared by pasteurization.
Salt may be added to the hydrolysate or to the liquid sauce to give a liquid sauce having a salt content of up to about 60% by weight based on the weight of dried matter. The liquid sauce may also be concentrated to produce a concentrate, the concentrate dried to a low moisture content to give a dry concentrate, and the dry concentrate milled to give a powdered solid seasoning. The present invention also relates to the solid seasoning prepared according to the above-described process.
The hydrolysate may also be dried to give a dried hydrolysate and the dried hydrolysate mixed with water, salt, and reducing sugars to give a base for an aromatizing agent for a culinary product in the form of a paste. The paste may have a dry matter content of from 35 to 55% by weight and contain, on a dry matter basis, from about 24 to 97% of the hydrolysate, about 2 to 40% salt, and about 1 to 4% reducing sugar.
The present invention also relates to a base for an aromatizing agent for a culinary product prepared according to the above-described process. The dried hydrolysate may be mixed with a sulphur containing amino acid or thiamine so that the paste contains, on a dry matter basis, from about 0 to 2% of the sulphur containing amino acid or thiamine. The paste may also be heated at a temperature of from between about 80xc2x0 and 150xc2x0 C. for a period of time of between about 1 minute and 4 hours. The paste may also be dried to a residual water level of up to about 2% to provide a base for an aromatizing agent for a culinary product as a dried powder.
In our U.S. Pat. No. 5,965,178, we describe a process or the production of a seasoning which comprises preparing a fermented protein Koji from a protein containing material and a carbohydrate, hydrolyzing the fermented protein Koji at a temperature between 15xc2x0 C. and 60xc2x0 C. an a pH of from 4.5 to 10 for a period of from 6 hours to 28 days characterized in that the protein containing material and the carbohydrate are inoculated with a culture of a lactic acid bacteria at an inoculation density of from 103 to 107 cfu/g of fermented protein Koji at either the fermented protein Koji stage or in the hydrolysis stage.
We have now surprisingly found that certain specific lactic acid bacteria are capable of imparting a specific characteristic note to the seasoning, for example, a meaty, seafood, or cereal note. Moreover, the note is stronger if the lactic acid bacteria inoculation takes place at the beginning of the fermentation step than if inoculation with the same lactic acid bacteria occurs after the fermentation step. The hydrolysate produced also has a very much stronger note than hydrolysates produced using other lactic acid bacteria. Without wishing to be bound by theory, we believe that during fermentation, the specific lactic acid bacteria produces specific enzymes that convert sulphur containing amino acid in the protein substrate, for example cysteine, into hydrogen sulphide that acts as a precursor to building blocks for the development of a meaty note.
For reasons of simplicity, the lactic acid bacteria capable of imparting a specific characteristic note to the seasoning that is stronger when it is inoculated at the beginning of the fermentation stage than if it is inoculated after the fermentation stage will be referred to in the description as the xe2x80x9cspecific lactic acid bacteria.xe2x80x9d Examples of suitable specific lactic acid bacteria are L. sake, L. plantarum, and L. cuvatus. It should be understood that, according to the invention, mixtures of two or more cultures of the specific lactic acid bacteria may be used, for example, mixtures of L. sake and L. plantarum, mixtures of L. sake and L. cuvatus, or mixtures of L. plantarum and L. cuvatus. 
It should also be understood that longer periods of time are generally required for hydrolysis at lower temperatures and shorter periods of time are required at higher temperatures.
The fermented Koji is prepared by a process similar to the preparation of a conventional soya sauce and includes, for example, inoculating a protein containing material and a carbohydrate with, in addition to a culture of the specific lactic acid bacteria, a culture of Aspergillus oryzae and/or Aspergillus sojae on a culture bed to form the fermented Koji. The specific lactic acid bacteria may be added before or after the culture of Aspergillus is added. If the specific lactic acid bacteria is added after the culture of Aspergillus, however, it should be added soon after the commencement of fermentation, generally within about 1 hour. Preferably the specific lactic acid bacteria is added, within about 30 minutes, more preferably within about 15 minutes, more preferably within about 5 minutes, and most preferably within about 1 minute.
The protein containing material is advantageously a plant protein material containing a high proportion of cysteine. Preferably, the plant protein material contains from about 0.5 to 3% cysteine by weight and more preferably from about 0.75 to 2% by weight. The protein containing material may be, for example, soya, wheat germ, corn gluten, rice gluten, or a mixture thereof. Preferably the plant protein containing material is wheat gluten, to produce an increased level of sulphide in the hydrolysate and, thus, an increased meaty note.
The degree of characteristic note, for example, a meaty, seafood, or cereal note may also be varied by varying the proportions of protein and carbohydrate in the Koji substrate. The Koji substrate may contain, for example, protein in an amount of from about 30 to 100%. Preferably the amount of protein is from about 70 to 90%. The plant protein containing material is advantageously cooked and preferably is used in solid particulate form to enable the mold of Aspergillus oryzae and/or Aspergillus sojae to grow on the surface of the particles and eventually penetrate into the particles. The particles of the plant protein material, which may be in the form of pellets, preferably have an average diameter of from about 2 to 10 mm, more preferably from about 3 to 8 mm, and most preferably from about 4 to 7 mm. The Koji is conveniently fermented in the solid state.
During the fermentation stage, the specific lactic acid bacteria grow rapidly and, by the end of the fermentation, dominate the flora at a level of between about 108 to 109 cfu/g along with the A. oryzae. The quality of the =Koji is therefore clean with respect to other possible contaminants. By adding the specific lactic acid bacteria at the beginning of the fermentation, the type of microflora present is controlled right from the start and there is no opportunity for contaminants to multiply. The high level of bacteria in the fermented Koji increases the protection against the growth of undesirable microorganisms in the subsequent hydrolysis.
The hydrolysis of the fermented protein Koji may be carried out in the presence of water and may be carried out in the absence of or in the presence of salt. Preferably, the hydrolysis is carried out in the absence of salt at a temperature from about 30xc2x0 to 37xc2x0 C. over a period of from about 2 to 5 days, in order to maximize the enzyme activity of L. sake, which leads to the production of a stronger meaty flavor in the hydrolysate. When salt is present, the amount of salt may be up to 100% by weight based on the weight of the fermented Koji. Advantageously, the hydrolysis is carried out with constant agitation. Optionally, a two-stage hydrolysis may be used, for example, a first stage hydrolysis at a temperature of from about 40xc2x0 to 25xc2x0 C. over a period of from about 1 to 48 hours followed by a second stage hydrolysis at a temperature of from about 25xc2x0 to 50xc2x0 C. over a period of from about 1 to 20 days.
If desired, additional protein, containing a high proportion of cysteine, for example, wheat gluten, may be added at the beginning of the hydrolysis stage to increase the meaty note.
At the end of the hydrolysis stage, the level of the reducing sugars is very low, i.e., usually less than about 0.3%. As a result of the low level of reducing sugars the maturation of the moromi can be eliminated. By eliminating maturation of the moromi the production time can be shortened by about 1 to 6 weeks.
Following the hydrolysis stage, the hydrolyzed fermented Koji, together with the culture of the specific lactic acid bacteria, may be pressed to separate a liquid sauce from a solid residue. Advantageously, the liquid sauce is pasteurized, for example, at a temperature of from about 90xc2x0 to 140xc2x0 C. for a period of from about 15 seconds to 30 minutes. The liquid sauce is then filtered to give a liquid seasoning. If desired, salt may be added either before or after pressing or filtering to give a product having a salt content of between about 0 and 60% by weight based on the weight of dried matter. If desired, the liquid sauce may be made into a powder for instance, by concentration; followed by drying, for example, by vacuum drying to a low moisture content; and finally milling into a powder to give a solid seasoning.
The hydrolysate produced by the process of the present invention may be used, in either liquid, paste or solid form, as a base for an aromatisation agent for culinary products. The paste may have a dry matter content of from about 35 to 55% by weight and is produced by drying the hydrolysate and mixing it with water, salt, reducing sugars, and optionally a sulphur containing amino acid or thiamine. The paste contains, on a dry matter basis, from about 24 to 97% of the hydrolysate, about 2 to 40% salt, about 1 to 4% reducing sugars, and from about 0 to 2% of a sulphur containing compound, for example, an amino acid such as cysteine or thiamine. If desired, the paste can be heated at a temperature of from about 80xc2x0 to 150xc2x0 C., preferably from about 90xc2x0 to 110xc2x0 C. for from about 1 minute to 4 hours, preferably from about 1 hour to 2 hours. The heated paste may afterwards be dried to a residual water level of up to about 2%.
The hydrolysates of the present invention may be used as body givers for culinary products in process flavor applications, for example, beef, seafood, cereal, and chicken flavors and as ingredients for HPP replacers. When the sauce powder is reconstituted in water, the product has a much lighter color, a strong flavor, and is more neutral with respect to the typical fermented note found in the standard wheat gluten sauce.